Yeah he's not a bad guy or anything, he's just (like many creatives) kind of self absorbed and gets some weird ideas or perspectives. He just assumes the worst and sees everything as a symbolic assault on him as a human, like you could see him at a party, offer him a diet coke, and he would assume you were trying to shame him and imply he was fat around his peers.

A lot of people have a tendency to wonder if the people giggling near them are giggling at them, Harmon just generally assumes they are. Certainly not a bad guy, and almost certainly just insecurities stemming from feeling isolated in a lot of ways.

He's pretty honest about his shortcomings as well, but just cyclically forgets to remember them and has meltdowns